Since the center of the brake cam is fixed, the corresponding points on the two brake shoes are equal to each other with respect to the amount of displacement of the brake drum, regardless of whether the cam turns through any angle.

However, due to the fact that the gap between the two sides of the hoof can not be adjusted in full, the two feet on the drum of the degree of compression is not equal, the original gap between the smaller side of the brake shoe on the normal braking force and friction Force is greater, so this brake at the beginning of use, is non-balanced.

However, after a long period of use, the drum unit pressure or the collar of the friction plate wear must be faster, so that the gap between the two sides are becoming the same, the corresponding normal reaction force is gradually equal, that is converted into balanced.